1. Field of the Invention
This invention relates to a corrosion-resistant titanium-base alloy material for use as an electrode substrate for use in electrolysis.
2. Description of the Prior Art
In recent years, insoluble metallic electrodes made by coating a metallic substrate with a platinum-group metal such as platinum or ruthenium or an oxide thereof have gained wide commercial acceptance as electrodes for use in the electrolysis of aqueous solutions of salts such as sodium chloride or sea water, aqueous solutions containing various acids such as sulfuric acid, nitric acid, hydrochloric acid or organic acids, and aqueous solutions containing alkalies. Pure titanium has been used as the metallic substrate.
When pure titanium is used as a material for an electrode substrate, the substrate surface sometimes is oxidized or is dissolved during the electrolysis of the various materials described above, particularly during the electrolysis of acidic aqueous solutions. Furthermore, in some cases, the substrate is corroded by acidic electrolyte solutions or solutions of the electrolysis product which penetrate through cracks or pinholes in the electrode coating layers. This accelerates the peeling off of or consumption of the electrode coating, and shortens the life of the electrode.
On the other hand, corrosion-resistant alloys consisting of titanium as a base and various other metals, for example, alloys of titanium and platinum-group metals (as disclosed in Japanese Patent Publication No. 6053/58) and an alloy of titanium and niobium (as disclosed in Japanese Patent Publication No. 15007/78) are known. It is also known to use a binary alloy consisting of titanium and zirconium, a platinum-group metal, niobium or tantalum as a substrate of an insoluble metallic electrode (as disclosed in Japanese Patent Publication No. 31510/72). However, these alloys and the substrate have poor acid resistance or bondability to electrode coatings, and are not entirely suitable from the standpoint of electrochemical durability.